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Test Code LAAPS1 LA/APS Comprehensive (Functional and Antigenic) Level 1 Package

Specimen Type

Blood

Container

4 light blue top tubes (3.2% sodium citrate) and 2 red top tubes

Preferred Volume

16 mL

Offsite Collection Instructions

  • Samples must be centrifuged at >1500 x g for 10 minutes at room temperature.
  • Carefully remove the plasma from the cells using a plastic transfer pipette avoiding the buffy coat.
  • Dispense the plasma into a plastic tube (glass is not acceptable) and centrifuge the plastic tube for a second centrifugation at >1500 x g for 10 minutes at room temperature.
  • Remove the top portion of the plasma being careful to leave a small amount of plasma at the bottom of the tube undisturbed (about 250mL). Then, aliquot the removed plasma into 4 plastic tubes containing a minimum of 1.0 mL of specimen in each tube.
  • The plasma samples must then be frozen at -20ºC.
  • Once solidly frozen they must be shipped on dry ice. Frozen plasma samples that have thawed in transit will be rejected.

Note: For clients who do not have access to dry ice do not freeze the specimen. Follow the centrifugation instructions or send the whole blood sample. It now becomes vital that the specimen arrives in the lab within three hours of collection.
 

Serum specimen should be centrifuged at >1500 x g for 10 minutes. Aliquot removed serum into 3 tubes containing minimum of 0.5 mL of specimen each. They may be sent refrigerated or frozen.
Note: Frozen serum samples that have thawed in transit will be rejected.

UCMC Collection Instructions

Specimens for this package may be collected and sent to the laboratory at any time

Availability

Functional lupus anticoagulant is performed 3 times a week Monday- Friday 1st shift only. Antigenic testing is performed on Tuesdays and Fridays 1st shift only.

Turnaround Time

4 days

STAT Availability

Not Available

Test Usage

The package includes both functional lupus anticoagulant (LA) testing and antigenic testing for detection of “antiphospholipid” antibodies.

Test Methodology

Functional LA testing employs clotting methodology. Antigenic testing is done by chemiluminescence method.

Additional Information

Note: Each of the three functional LA testing systems now in use employ a heparin-neutralizing agent capable of neutralizing levels of heparin employed therapeutically in patients.  However, with the advent of direct thrombin inhibitors, these tests will no longer function properly to detect possible LA’s.  Accordingly, if the aPTT-LA screen is prolonged, a TT will be performed.  If this TT is prolonged, then a TT preceded by incubation of the plasma with heparinase will be performed to determine if heparin might be the cause of the prolongation. In contrast to plasma anticoagulated with unfractionated or low molecular weight heparin, plasma anticoagulated with direct thrombin inhibitors will not show a shortening of the TT following heparinase incubation.  Accordingly in such a situation, further LA functional testing will not be performed.

 

All 3.2% sodium citrate light blue top tubes require a ratio of 9 parts blood to 1 part anticoagulant (example: a 3.0 mL tube requires 2.7 mL blood added to 0.3 mL of anticoagulant).

CPT Code

86147, 86146, 85613, 85670, 85732, 85597, 85705

Test Includes

The package includes both functional lupus anticoagulant (LA) testing and antigenic testing for detection of “antiphospholipid” antibodies. The package includes functional LA testing by three independent systems—one based on a dilution of the Russell viper venom time (Dilute Russell Viper Venom Time, or “DRVVT”), one based on a dilution of the activated partial thromboplastin time (“PTT-LA”), and one based on a dilution of the prothrombin time (“dPT”). In each case a screening test is performed. If results in the screen are sufficiently prolonged, testing will proceed to a mixing study. If there is not sufficiently strong correction of the abnormality in the mixing phase, testing will then proceed to a confirmatory phase for that testing system. While the actual number of seconds of clotting times in the various phases of the specific testing systems necessarily varies as a function of reagent lot changes, the criterion for determination of normal vs abnormal with respect to detection of a LA remains constant: A 99th percentile upper limit for the normal reference population is determined for the confirmatory phase in each testing system at the time of lot changes, and is used as the basis for reporting of results in EPIC
 

The package also includes testing for the presence of IgG and IgM antibodies directed against beta-2 glycoprotein I (beta-2 GPI). Because the conformational presentation of beta-2 GPI determines whether or not a particular patient antibody will recognize it as an antigenic target, the beta-2 GPI is employed in two different forms. The first employs the beta-2 GPI directly attached to solid phase, and is termed the IgG or IgM “anti- beta-2 GPI” assay. The second employs cardiolipin directly attached to the solid phase, with beta-2 GPI then secondarily being bound to the cardiolipin, and is termed the IgG or IgM “anti-cardiolipin” assay.

Reference Range

DRVVT Screen: <39.9 seconds
PTT-LA Screen: <41.8 seconds
dPT Screen: <49.3 seconds
Anticardiolipin IgG <20.1 CU
Anticardiolipin IgM <20.1 CU
Beta-2 GPI IgG <20.1 CU
Beta-2 GPI IgM <20.1 CU

Fee Code

 30585613, 30185732, 30085705, 30086147, 30186147, 30086146, 30186146,

Synonyms

Lupus; LA; APS; LA/APS; APS/LA; Dilute Russell Viper Venom Screen (DRVVT); PTTLA; PTT with lupus sensitive reagent; Dilute Prothrombin Time (DPT); Anticardiolipin Antibodies; B2GP; Beta-2 Glycoprotein I Antibodies; LAAPS1